Search inside publication
Groundwater flow modeling using iMOD for Barva and Colima aquifers in the central valley of Costa Rica : validation of a conceptual model using tracer data
A stationary numerical model of groundwater flow was developed using iMOD to better understand the recharge processes within Barva and Colima aquifers (BCS), located in the northwestern region of the Central Valley of Costa Rica. Lithological information was used to develop conceptual model representing the complexity of the system, defined as high transmissivities, low storage capacity, and steep hydraulic gradients. Due to the lack of more detailed lithological and hydrometric data to perform robust calibrations, the system was studied by analyzing water flux dynamics using the iMOD particle tracer and water balance tools. The validation process was done by comparing the results of each simulation with the potential recharge elevation (PRE) derived from the ages of existing noble gases (tritium/helium) at different wells and springs in the system. Tracer estimations indicate a groundwater age (GWA) ranging from 2.3 to 71 years. Based on the tracer information, two hypotheses of PRE were evaluated. The first scenario (H01), with a PRE between 1,500 to 2,500 m a.s.l., and a second one (H02), with a PRE between 1,300 to 1,500 m a.s.l. Results from H01 were the most reliable: 77% of the particles dropped in the PRE were captured by the Lower Colima aquifer, with a GWA ranging from 1 to 45 years. Although the results reflect the dynamic complex fluxes, more information is needed to understand the influence of surface water and recharge rates on groundwater levels in order to improve and calibrate the model as a reliable water management tool.
Liquefaction flow slides in large flumes
Liquefaction flow slides in sand have been investigated during an extensive experimental research programme during the period 1973–1977 on behalf of the design of the storm surge barrier in the Oosterschelde estuary. The programme included more than a hundred tests in large- and medium-sized flumes on submerged, loosely packed sand bodies. Each sand body had a horizontal surface and a very steep, supported slope as initial boundaries. Retrogressing liquefaction flow slides with high retrogression velocity and large retrogression distance occurred in several tests with very loosely packed sand. Retrogression velocities and distances in the other tests were just a fraction of those in first mentioned tests, although liquefaction occurred in some of them. The test set-up, measurements and results of the tests are described in this paper. An interpretation of the liquefaction flow slide process as a sequence of several interacting sub-processes is presented as well. Finally, tentative scaling rules are given and compared with observations.
Temperature buffering by groundwater in ecologically valuable lowland streams under current and future climate conditions
Groundwater seepage influences the temperature of streams and rivers by providing a relatively cool input in summer and warm input in winter. Because of this, groundwater seepage can be a determining factor in the provision of suitable water temperatures for aquatic biota. Climate warming affects stream and groundwater temperatures, and changes the thermal characteristics of streams leading to the potential disappearance of habitats. In this study the importance of groundwater for the temperature of two Dutch lowland streams and its possible role in mitigating the effects of climate change was determined by combining field measurements and a modelling experiment. Stream temperature measurements using fibre optic cables (FO-DTS) and sampling of 222Rn were done to map localized groundwater inflow. Several springs and seepage ‘hot-spots’ were located which buffered the water temperature in summer and winter. A stream temperature model was constructed and calibrated using the FO-DTS-measurements to quantify the energy fluxes acting on stream water. This way, the contribution to the stream thermal budget of direct solar radiation, air temperature and seepage were separated. The model was then used to simulate the effects of changes in shading, groundwater seepage and climate. Shading was shown to be an important control on summer temperature maxima. Groundwater seepage seemed to buffer the effect of climate warming, potentially making groundwater dominated streams more climate robust. Protecting groundwater resources in a changing climate is important for the survival of aquatic species in groundwater-fed systems, as groundwater seepage both sustains flow and buffers temperature extremes.
Voortgangsbericht KPP-project Versterking Onderzoek Waterveiligheid (no. 4)
Samen met enkele andere partijen doet Deltares voor Rijkswaterstaat onderzoek op het gebied van waterveiligheid. Dit gebeurt in het kader van het KPP-project Versterking Onderzoek Waterveiligheid, waarbij KPP staat voor kennis primaire processen. Rijkswaterstaat gebruikt de uitkomsten van het onderzoek om zijn primaire proces rondom waterveiligheid te verbeteren. Bij deze verbeteringen gaat het om kostenbesparingen bij aanleg, beheer en onderhoud, en ook om betere risicobeheersing en versterking van het imago van Rijkswaterstaat. Het merendeel van de projecten wordt in NKWK-kader uitgevoerd, dus samen met en met medefinanciering van andere partijen uit de sector, zoals STOWA, individuele waterschappen en TU Delft. Dit vierde voortgangsbericht brengt de werkzaamheden in beeld die we in 2018 hebben uitgevoerd. Daarbij geven we een inschatting van de meerwaarde van de projecten voor Rijkswaterstaat. Bij sommige projecten geeft Rijkswaterstaat ook zelf aan waarom het project van belang is.
Flood resilience of critical infrastructure : approach and method applied to Fort Lauderdale, Florida
In order to increase the flood resilience of cities (i.e., the ability to cope with flood hazards), it is also crucial to make critical infrastructure functions resilient, since these are essential for urban society. Cities are complex systems with many actors of different disciplines and many interdependent critical infrastructure networks and functions. Common flood risk analysis techniques provide useful information but are not sufficient to obtain a complete overview of the effects of flooding and potential measures to increase flood resilience related to critical infrastructure networks. Therefore, a more comprehensive approach is needed which helps accessing knowledge of actors in a structured way. Fort Lauderdale, Florida, United States has suffered from flood impacts, especially from disruptions in critical infrastructure. This paper shows how shared insight among different sectors and stakeholders into critical infrastructure resilience and potential resilience-enhancing measures was obtained using input from these actors. It also provides a first quantitative indication of resilience, indicated by the potential disruption due to floods and the effect of measures on resilience. The paper contributes to the existing literature on resilience specifically by considering the duration of disruption, the inclusion of critical infrastructure disruption in flood impact analysis, and the step from resilience quantification to measures.
Contribution of potential evaporation forecasts to 10-day streamflow forecast skill for the Rhine River
Medium-term hydrologic forecast uncertainty is strongly dependent on the forecast quality of meteorological variables. Of these variables, the influence of precipitation has been studied most widely, while temperature, radiative forcing and their derived product potential evapotranspiration (PET) have received little attention from the perspective of hydrological forecasting. This study aims to fill this gap by assessing the usability of potential evaporation forecasts for 10-day-ahead streamflow forecasting in the Rhine basin, Europe. In addition, the forecasts of the meteorological variables are compared with observations. Streamflow reforecasts were performed with the daily wflow_hbv model used in previous studies of the Rhine using the ECMWF 20-year meteorological reforecast dataset. Meteorological forecasts were compared with observed rainfall, temperature, global radiation and potential evaporation for 148 subbasins. Secondly, the effect of using PET climatology versus using observation-based estimates of PET was assessed for hydrological state and for streamflow forecast skill. We find that (1) there is considerable skill in the ECMWF reforecasts to predict PET for all seasons, and (2) using dynamical PET forcing based on observed temperature and satellite global radiation estimates results in lower evaporation and wetter initial states, but (3) the effect on forecasted 10-day streamflow is limited. Implications of this finding are that it is reasonable to use meteorological forecasts to forecast potential evaporation and use this is in mediumrange streamflow forecasts. However, it can be concluded that an approach using PET climatology is also sufficient, most probably not only for the application shown here, but also for most models similar to the HBV concept and for moderate climate zones. As a by-product, this research resulted in gridded datasets for temperature, radiation and potential evaporation based on the Makkink equation for the Rhine basin. The datasets have a spatial resolution of 1:21:2 km and an hourly time step for the period from July 1996 through 2015. This dataset complements an earlier precipitation dataset for the same area, period and resolution.
Decision support for low-emission policy pathways under uncertainty
This essay explores how decision-making under severe (deep) uncertainty (DMDU) approaches can be used to support decision-making on low-emission strategies in order to guide NDCs (Nationally determined contributions), taking into account uncertainties. We focus on dynamic adaptive policy pathways (DAPP) as an approach that can facilitate the design of policy pathways with low greenhouse gas (GHG) emissions.
Current insights into the effectiveness of riparian management, attainment of multiple benefits, and potential technical enhancements
Buffer strips between land and waters are widely applied measures in diffuse pollution management, with desired outcomes across other factors. There remains a need for evidence of pollution mitigation and wider habitat and societal benefits across scales. This paper synthesizes a collection of 16 new primary studies and review papers to provide the latest insights into riparian management. We focus on the following areas: (i) diffuse pollution removal efficiency of conventional and saturated buffer strips, (ii) enhancing biodiversity of buffers, (iii) edge-of-field technologies for improving nutrient retention, and (iv) potential reuse of nutrients and biomass from buffers. Although some topics represent emerging areas, for other well-studied topics (e.g., diffuse pollution), it remains that effectiveness of conventional vegetated buffer strips for water quality improvement varies. The collective findings highlight the merits of targeted, designed buffers that support multiple benefits, more efficiently interrupting surface and subsurface contaminant flows while enhancing diversity in surface topography, soil moisture and C, vegetation, and habitat. This synthesis also highlights that despite the significant number of studies on the functioning of riparian buffers, research gaps remain, particularly in relation to (i) the capture and retention of soluble P and N in subsurface flows through buffers, (ii) the utilization of captured nutrients, (iii) the impact of buffer design and management on terrestrial and aquatic habitats and species, and (iv) the effect of buffers (saturated) on greenhouse gas emissions and the potential for pollution swapping.
Outcome DAMSAFE project in Karnataka
In cooperation with the Karnataka Water Resources Department (KaWRD) a pilot project, called DAMSAFE, is recently completed at the Bhadra dam and reservoir, located in Karnataka (India). In DAMSAFE an operational monitoring and forecasting system is implemented and the results are demonstrated to the dam operator. The overarching goal of the pilot project is to contribute to enhancing dam safety and water management in India. The innovative technologies, integrated in DAMSAFE, are: PS-InSAR satellite measurements, in-situ measurements and the Delft-FEWS software platform. Delft-FEWS is used to integrate global weather forecasting and (measurement) data from different sources with automatic computations using different hydrology, hydraulic and geotechnical numerical models. The system supplies information on forecasting of inflow and water levels in the reservoir that can be used for Real Time Control (RTC) of reservoir operation. Based on water pressure measurements in the dam body and dam foundation the stability of the dam is calculated real time. In future, the forecasting of water reservoir levels allows for forecasting of dam stability. This information can be used to control flood risk and for emergency response actions.
International Dam Safety Conference 2019 (13-14 February 2019, Bhubaneswar, Odisha, India)